Switched-Current Line Driver Common-Mode Power Reduction
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Solution Overview
Problem
High power consumption in line drivers for high-speed serial interfaces, particularly due to increased power usage in complementary current driving and common-mode current flow, which is exacerbated by decreasing supply voltages and the need for multiple drive and pre-emphasis levels, leading to undesirable power consumption even at maximum supported levels.
Innovation Solution
A method to reduce power consumption in differential switched-current line-drivers by eliminating output current not contributing to the differential signal, achieved through a training phase to determine required output current, followed by gradual elimination of redundant common-mode current while maintaining differential current, using a segmented current driver with cells in controllable states to manage differential and common-mode currents independently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complementary current driving topology is used to meet speed and impedance requirements, then signal transmission quality is improved, but power consumption increases significantly
Solution Approach 1:
The current driver is divided into multiple independently controllable current source segments. Each segment can be individually enabled or disabled based on the required drive level, allowing the total current to be precisely controlled. This segmentation enables the system to use only the necessary current for each operating condition, reducing power consumption while maintaining signal transmission quality.
Solution Approach 2:
The system dynamically adjusts the total output current by enabling or disabling specific current source segments based on training results and operating conditions. This dynamic current control allows the driver to adapt its power consumption to the actual signal requirements, rather than operating at fixed maximum current levels.
2Adaptability or versatility
If multiple drive levels and pre-emphasis levels are supported, then adaptability is improved, but power consumption increases even at maximum supported levels
Solution Approach 1:
The current driver is divided into multiple independently controllable current source segments. Each segment can be individually enabled or disabled based on the required drive level, allowing the total current to be precisely controlled. This segmentation enables the system to use only the necessary current for each operating condition, reducing power consumption while maintaining signal transmission quality.
Solution Approach 2:
The system changes the operating parameters by dynamically adjusting the total output current through selective enabling/disabling of current source segments. This parameter adjustment allows the driver to optimize power consumption for each specific drive level and pre-emphasis level configuration.
3Reliability
If common-mode current flows through terminations to maintain common-mode voltage, then common-mode signal requirements are met, but unnecessary power is consumed
Solution Approach 1:
The invention extracts and eliminates the common-mode current component from the output. By using a differential current driving approach where equal and opposite currents are sourced and sunk, the common-mode current is cancelled out, leaving only the useful differential current. This removes the wasteful common-mode power consumption while maintaining differential signal integrity.
Solution Approach 2:
The system uses asymmetric current routing where one current source drives current in one direction while another drives equal current in the opposite direction. This asymmetric configuration ensures that common-mode currents cancel out, eliminating unnecessary power consumption in the terminations.
Data Source
AI summary
A differential switched-current line-driver implements a method to reduce power consumption by eliminating output current that does not contribute to the required differential output signal. This output current is used for example during a training phase, and the current elimination can take place after the training phase is complete.